base64.cpp revision 72961230a5890071bcca436eb5630172ce84ec41 
1/*
2 * Copyright (C) 2010 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17#include "base64.h"
18
19#include "ABuffer.h"
20#include "ADebug.h"
21
22namespace android {
23
24sp<ABuffer> decodeBase64(const AString &s) {
25    if ((s.size() % 4) != 0) {
26        return NULL;
27    }
28
29    size_t n = s.size();
30    size_t padding = 0;
31    if (n >= 1 && s.c_str()[n - 1] == '=') {
32        padding = 1;
33
34        if (n >= 2 && s.c_str()[n - 2] == '=') {
35            padding = 2;
36        }
37    }
38
39    size_t outLen = 3 * s.size() / 4 - padding;
40
41    sp<ABuffer> buffer = new ABuffer(outLen);
42
43    uint8_t *out = buffer->data();
44    size_t j = 0;
45    uint32_t accum = 0;
46    for (size_t i = 0; i < n; ++i) {
47        char c = s.c_str()[i];
48        unsigned value;
49        if (c >= 'A' && c <= 'Z') {
50            value = c - 'A';
51        } else if (c >= 'a' && c <= 'z') {
52            value = 26 + c - 'a';
53        } else if (c >= '0' && c <= '9') {
54            value = 52 + c - '0';
55        } else if (c == '+') {
56            value = 62;
57        } else if (c == '/') {
58            value = 63;
59        } else if (c != '=') {
60            return NULL;
61        } else {
62            if (i < n - padding) {
63                return NULL;
64            }
65
66            value = 0;
67        }
68
69        accum = (accum << 6) | value;
70
71        if (((i + 1) % 4) == 0) {
72            out[j++] = (accum >> 16);
73
74            if (j < outLen) { out[j++] = (accum >> 8) & 0xff; }
75            if (j < outLen) { out[j++] = accum & 0xff; }
76
77            accum = 0;
78        }
79    }
80
81    return buffer;
82}
83
84static char encode6Bit(unsigned x) {
85    if (x <= 25) {
86        return 'A' + x;
87    } else if (x <= 51) {
88        return 'a' + x - 26;
89    } else if (x <= 61) {
90        return '0' + x - 52;
91    } else if (x == 62) {
92        return '+';
93    } else {
94        return '/';
95    }
96}
97
98void encodeBase64(
99        const void *_data, size_t size, AString *out) {
100    out->clear();
101
102    const uint8_t *data = (const uint8_t *)_data;
103
104    size_t i;
105    for (i = 0; i < (size / 3) * 3; i += 3) {
106        uint8_t x1 = data[i];
107        uint8_t x2 = data[i + 1];
108        uint8_t x3 = data[i + 2];
109
110        out->append(encode6Bit(x1 >> 2));
111        out->append(encode6Bit((x1 << 4 | x2 >> 4) & 0x3f));
112        out->append(encode6Bit((x2 << 2 | x3 >> 6) & 0x3f));
113        out->append(encode6Bit(x3 & 0x3f));
114    }
115    switch (size % 3) {
116        case 0:
117            break;
118        case 2:
119        {
120            uint8_t x1 = data[i];
121            uint8_t x2 = data[i + 1];
122            out->append(encode6Bit(x1 >> 2));
123            out->append(encode6Bit((x1 << 4 | x2 >> 4) & 0x3f));
124            out->append(encode6Bit((x2 << 2) & 0x3f));
125            out->append('=');
126            break;
127        }
128        default:
129        {
130            uint8_t x1 = data[i];
131            out->append(encode6Bit(x1 >> 2));
132            out->append(encode6Bit((x1 << 4) & 0x3f));
133            out->append("==");
134            break;
135        }
136    }
137}
138
139}  // namespace android
140